Help interpreting OBDII data please

henleyryan

henleyryan

henleyryan

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Joined
4 Oct 2004
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228
Location
Northants
Hi,

I'm currently driving a 2011 Citroen C4 Picasso 2.0 petrol automatic which had an issue a few months ago with error code P0170. I took the car to the garage and they said it was probably just a bit of dirty fuel so reset it. More recently the car went into limp mode and came up with error code p1337 (which google says is a misfire on cylinder 1). The car went back to the garage and they said it was due to the injectors so replaced (at a fair chunk of money) all four injectors and said the car was fixed. I drove the car home and the first half of the journey it seemed to be driving better that it ever had (although this could have just been my mind playing tricks, placebo affect type of thing) but half way home the original P0170 came back and the car felt slightly more sluggish again. The garage collected that car and a week later said "it was the electronic ignition needed cleaning", which doesn't sound right to me. Anyways, I collected the car and drove it home again, same thing on the journey home P0170 comes back.

I don't trust the garage anymore so want to look at it myself. My gut instinct tells me that it is overfuelling for some reason, based on the engine feels very sluggish to get going, the coolant temperature seems lower than I would expect, and the average consumption doing my city driving is about 13l/100km.

I would be really graetful if anyone could have a look through my recorded OBDII data and let me know if anything seems out of place, that may point me in the direction of the next thing to check/replace.

Car Data.xlsx

1drv.ms 1drv.ms
 
@henleyryan

I don't have the expertise to interpret the obd2 data, but a couple of questions:

You mentioned the P1337 code relates to a misfire on cylinder 1, but what does the P0170 fault code, which has returned, relate to?

Also, have the basics below been covered?

Spark plugs in good condition and gapped correctly?

Coil or coil packs working correctly?

Maf sensor clean?

Air filter fairly new and not filthy?

That sort of thing.


Many garages don't bother with proper fault investigation nowadays, they just run a diagnostic and change some parts.

Your gut instinct may well be right. The ECU may be overfuelling to keep the engine running due to another problem, so the efficiency goes out of the window and you lose power but the engine runs.

I'd start with the basics, hit the Citroen owners club forums (if there are some) and go from there.
 
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If I could read the data I could probably help but that spreadsheet has formatted it into gobbledygook I can't make head nor tail of..
Reset the data and go back into a live data page and look at long and short term fuel trims while it is running at idle and warm.
Short term trim is where ecu tries to react instantly to get the fuel ratio to a desired setpoint, if the short term trim remains one side of positive or negative for a set period of where it thinks it should be (adding or taking away fuel) it will bring in the long term trim to compensate to bring the short term back to setpoint.
For eg if car was "running rich" it would result in a neg short term trim as it tries to take fuel out to lean it off.. if it stays rich it will start to use long term trim in a negative direction until short term comes back to setpoint..
If it reaches the limit of its adjustment... on comes the CEL. to say there is an issue.
Caveats!!!
The sensors may also be lying!
Its not going to be a five min job for someone who doesn't know what he's looking for..
It could be rich or lean and it could be because a sensor is failing, or another thing totally unrelated to the sensor causing it to read wrong, like its shorted out and pegged to its min/max output for eg. Or another sensor entirely telling it to trim the fuel for another reason.. like water temp being cold when its actually hot. Or it could be a dirty /failing MAF sensor giving it the wrong data on how much air is going in the engine and its trying to add fuel to that wrong air mixture..
There's quite a lot it "could be"
It could even be unrelated to emissions entirely and that code is a symptom from another cause, for eg if it does misfire because the coil pack is dying, it again will throw out the emissions sensor data.

Freeze frame data is also useful as it tells you all the sensors readings at the point it decided to throw a wobbler..

Dirty fuel and cleaning the electronic ignition.. lol. Take it to an actual garage not parts changers would be my best advice.
 
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